Related Experiment Video
Updated: Jan 17, 2026

Muscle Function Obtained with Motion Mode Ultrasound and Surface Electromyography during Core Endurance Exercise
Published on: August 25, 2022
Sex-related differences in core muscle morphology and activation in amateur CrossFit® athletes: An ultrasound imaging
Álvaro Marco-Serrano1, Alejandra Cazorla-Rincón1, Jorge Hugo Villafañe1
1Faculty of Medicine, Health and Sports, European University of Madrid, Villaviciosa de Odón, Madrid, Spain.
Background:
CrossFit® is a high-intensity functional training modality that integrates resistance exercises, weightlifting, and aerobic conditioning. Core musculature plays a critical role in ensuring spinal stability, force transmission, and injury prevention.
Aim:
This study aimed to compare abdominal muscle thickness and inter-recti distance (IRD) at rest and during contraction in male and female CrossFit® athletes using ultrasound imaging (USI).
Methods:
A cross-sectional study was conducted on 58 amateur CrossFit® athletes (29 males, 29 females) who trained at least five times per week. USI was used to assess the thickness of the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and transversus abdominis (TrAb) at rest and during contraction. Statistical analyses compared muscle thickness between sexes.
Results:
Males exhibited significantly greater RA, IO, and TrAb thickness at both rest and contraction (p = 0.001), whereas females demonstrated a significantly higher percentage change in TrAb thickness (p = 0.046), indicating greater relative activation. No significant differences were observed in EO thickness or IRD.
Conclusions:
Males showed greater core muscle thickness, while females exhibited a higher activation capacity in the TrAb. These findings suggest sex-specific adaptations in core musculature, which have implications for tailored training and injury prevention strategies in CrossFit® athletes.
Related Concept Videos
Imaging Studies II: Ultrasonography
Ultrasonography
During an ultrasonography procedure, a handheld device called...
Exercise and Muscle Performance
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
Muscles of the Thorax
The diaphragm is at the core of thoracic musculature, the primary muscle involved in breathing. This expansive, dome-shaped muscle marks the division between the thoracic and abdominal cavities. It...
Axial and Appendicular Muscles
Axial Muscles
Axial muscles, situated along the body's midline, are intricately connected to the axial skeleton, which includes the skull, spine, ribs, and sternum. These muscles facilitate facial expressions and...
Classification of Skeletal Muscle Fibers
Slow-Twitch Muscle Fibers
Slow oxidative, muscle fibers appear red due to large numbers of capillaries and high levels of...

